Some kinds of chips must be fault tolerant. They must continue to operate correctly, even when errors occur. Some kinds of errors occur from time to time, such as when an alpha particle or a power supply fluctuation causes a data bit to change value. Such errors are known as soft errors. Errors can also occur consistently, such as when a manufacturing defect or a process of wearing out causes signal wires within the chip to be stuck at a 1 or 0, shorted to another wire, or broken. Such errors are known as hard errors. Any errors would cause a conventional chip to fail.